Not too many years ago, it was nearly impossible to imagine a phone, computer, camera, video camera, arcade, calendar and MP3 player combined into a single handheld device. Now that we have these devices, it seems just as difficult to imagine living without them.

Apple's iPhone isn't so much a cellphone as it is a life companion. With iPhones we play games while waiting for appointments, capture moments on video, listen to music or novels while commuting, and engage with friends via phone, text messaging and social media. We plan our schedules, make dinner reservations and figure out how to get from place to place.

Since many of the iPhone's capabilities can be discovered through everyday use, lots of users believe that they have their phones all figured out. However, the device is tricky -- it boasts some features that are still unknown to even the most ardent Apple fans.

A few once-hidden iPhone functions have made their way into the spotlight. For example, screen shots: You probably know by now that you can capture an image of your iPhone's screen by pressing the home and power buttons simultaneously.

If you do a lot of texting, you may also know that you can turn off the message preview on your SMS alerts by going to Settings > Notifications > Messages and switching off the toggle next to "Show Preview." This is a popular option for those who don't want wandering eyes to read their text messages on their unattended phone.

Still, when I took a poll of my iPhone-user friends, I was surprised to discover that many were unaware of one of my favorite features: the quick scroll-up. When you find yourself at the bottom of a lengthy article or your iTunes library, you don't have to manually scroll back to the top of the page. Simply tap the time at the top of the screen (as shown in the image here) to instantly get back to the beginning. This trick saves a lot of time -- and thumb power.

Whether you have the iPhone 3, the iPhone 5, or something in between, there are simple ways to get more out of your smartphone investment. Take a look at these subtle but handy iPhone tricks and see if there's a way to use your phone that's new to you.

Already knew all these tricks? Share your favorite iPhone tips in the comments.

You've likely experienced the frustration that occurs when your iPhone can't decide which way is up. As you change sitting positions or lie down, it switches back and forth from portrait to landscape, regardless of whether you want it to stay in one place.

Stop this pesky screen rotation by first double-clicking the home button, which will display a list of recently opened apps. Swipe the list from left to right. This will reveal a set of music controls and a gray square with a circular arrow on the left. Tap that gray square and you'll see a message on the bottom that says "Portrait Orientation Locked." Your screen will no longer flip. Note that the screen cannot be locked into landscape mode, only portrait.

Most people don't regularly need a scientific calculator, and for them the standard iPhone calculator is good enough for everyday use. For those that need it, though, the iPhone does come with the scientific version. Simply go into the iPhone calculator and turn the phone to landscape mode to use it. Keep in mind that if your phone is locked into portrait mode, you must first unlock it to use the scientific calculator.

Stay on schedule with a full calendar view of your weekly plans. First enter the built-in iPhone calendar app in portrait mode. When you see the monthly view, tilt the phone into landscape mode. The monthly view will transform into a detailed display of your scheduled events for the week. The events are color-coded according to work/home, etc. (Again, remember to unlock portrait mode before using this feature.)

As a former BlackBerry user, I was a bit disappointed that my new iPhone didn't have a blinking light to silently inform me when a message was waiting. As it turns out, I was wrong. The LED camera light on the back of the iPhone can be set to flash when messages are received. To set yours, go to Settings > General > Accessibility. Under the Hearing category, switch on the toggle next to "LED Flash for Alerts."

Want a quick route to a website that you visit daily? You don't have to enter Safari every time you want to access it -- instead, turn that website into an app that you can access from your home screen. To do this, visit the page in Safari and tap the menu button at the bottom of the screen (it looks like a rectangle with an arrow coming out of it). Select the button that says "Add to Home Screen" and give the app a name.

The iPhone camera is pretty good, but some environments don't lend themselves to quality picture taking. With high-dynamic range (HDR) photography, the camera alters the image as it is being taken. The result is a photo that is the best possible quality, given your environment.

In HDR mode, the camera takes three pictures in rapid succession. Each image uses a different level of exposure: one for dark areas, one for light and one for midtones. After taking all three, the iPhone takes the best qualities of each image and stitches them together to produce a single high-quality image. If you're not happy with the final result, the phone saves both HDR and non-HDR versions of the picture.

To turn on this setting, select Options when the phone is in camera mode and turn on the HDR toggle. Note that this mode is best for up-close and outdoor portraits, and in dark environments (without flash). Do not use HDR in bright, sunlit conditions or when moving.

With the "Reply With Message" function, you can respond to a caller with a text message when you're unable to answer the phone.

When you receive a call, you should see a phone icon next to the green Answer button. Swipe up on that icon and select "Reply With Message." You'll see a list of three messages, one of which you can choose to instantly send to the caller. There's also an option for you to create a custom message at the time of the call. While you send the text message, the caller is directed to voice mail.

To personalize a pre-written message, go to Settings > Phone > Reply With Message. You can replace any of the listed messages with one of your own, as in the image on the left.

With Safari's Reading List, you can tag pages you want to save and read them later. When you want to save a page, tap the menu button at the bottom of the screen and select "Add to Reading List." To access it later, enter Safari and select Bookmarks > Reading List.

Apple's iPhone lends itself to global languages. Whether you're bilingual or simply want to describe your favorite ethnic food, you can type with accuracy. Simply hold your finger down on the letter you want to change. A variety of versions of that letter in different languages will appear.

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